CVE-2026-98990: namespace: check a submount for references right before unmounting it
Noroxi assessment
Priority: Monitor (action score 0/100)
- The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
- Probability of exploitation in the next 30 days: 0.18% (FIRST EPSS).
- Fixed version: Linux Linux 18902a23ef36f83d32bafc58ae2484e6bb4bb8ef, 32bf92416614a1e3ff3524fc6b780259c7aad3ef, 361f59e7f3f9a219fb5567bf9abc8482a154a399; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 Release Notes; azl3 kernel 6.6.159.1-1 on Azure Linux 3.0 6.6.161.1-1.
- Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).
Low priority for now. Upgrade to Linux Linux 18902a23ef36f83d32bafc58ae2484e6bb4bb8ef, 32bf92416614a1e3ff3524fc6b780259c7aad3ef, 361f59e7f3f9a219fb5567bf9abc8482a154a399; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 Release Notes; azl3 kernel 6.6.159.1-1 on Azure Linux 3.0 6.6.161.1-1 or later.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
In the Linux kernel, the following vulnerability has been resolved: namespace: check a submount for references right before unmounting it shrink_submounts() and mark_mounts_for_expiry() first collect all the mounts they are allowed to unmount and then unmount them. Whether a mount is busy is decided by propagate_mount_busy() on the tree. But unmounting the first mount changes the tree that the second one propagates into. propagate_umount() moves a surviving overmount off a copy it unmounts and mounts it where the copy was mounted. If that's where the propagated copy of the second victim is looked up the overmount becomes a candidate of the second umount_tree(). It's childless and so trim_one() commits it without looking at its reference count. So a synchronous umount pulls out a busy mount that is in use somewhere else and marks it MNT_SYNC_UMOUNT while it has users: umount2(/tmp/plshrink/p1, 0) = 0 errno 0 cwd is (unreachable) The same two umounts requested one after the other fail with EBUSY. This needs a mount with MNT_SHRINKABLE, i.e., automounted submounts of NFS, AFS and CIFS or the tracefs mount below debugfs. Bind mounts inherit the flag. Check each mount right before it is unmounted under the same hold of namespace_sem and mount_lock as the umount itself. Make sure that the algorithm stays linear.
- Published
- Oct 23, 2026
- Updated
- Oct 30, 2026
- EPSS
- 0.1% · 8th percentile
- CWE
- —
Report tools
Action score
0
Monitor
Low priority for now.
- CVSS
- 0 / 40 · —
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.1%
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- No public exploit code on record
- A fix has been released
If any of these changes, we'll tell you in the daily email digest.
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Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
—
Versions reported by the vendor
Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.
Linux Linux
- 5e6ef5ef6eaf690faad3a7c6c665ebf45d7b6ccf, 839d42687dfce0ed0ea2c6bd8d707cc0e276fbe7, 808e83e5add13152bd4a88346487de68395c136b, 6de9d08a9718ee9c12ba6343c50141c2d633e3dc, 4.11affected
- 1064f874abc0d05eeed8993815f584d847b72486 and later · before cda0c4e502a0f74a191471ce100fb061e5ab35d6affected · git
- 1064f874abc0d05eeed8993815f584d847b72486 and later · before 3f55f71291e4332983cd63b288d1f2be3c9c08fcaffected · git
- 1064f874abc0d05eeed8993815f584d847b72486 and later · before 361f59e7f3f9a219fb5567bf9abc8482a154a399affected · git
- 1064f874abc0d05eeed8993815f584d847b72486 and later · before f6394281834492c6516a405a348b545ae698a331affected · git
- 1064f874abc0d05eeed8993815f584d847b72486 and later · before 6e4012e571867868b545c91ca9d6095fdb709907affected · git
- 1064f874abc0d05eeed8993815f584d847b72486 and later · before d73f04e92c1aab78d96ac6cadb234c8a3a373d22affected · git
- 1064f874abc0d05eeed8993815f584d847b72486 and later · before 18902a23ef36f83d32bafc58ae2484e6bb4bb8efaffected · git
- 1064f874abc0d05eeed8993815f584d847b72486 and later · before 32bf92416614a1e3ff3524fc6b780259c7aad3efaffected · git
- 4.1.40 and later · before 4.2affected · semver
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | linux | from 0 | — |
| Debian:13 | linux | before 6.12.113-1 | 6.12.113-1 |
| Debian:14 | linux | before 7.2.11-1 | 7.2.11-1 |
Same product
linux: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation40Plan
- CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment40Plan
- CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()40Plan
Published before and after this one in the same product
- ← EarlierCVE-2026-98988Oct 23, 2026 · namespace: keep covered mounts covered in OPEN_TREE_NAMESPACE35Monitor
- ← EarlierCVE-2026-98989Oct 23, 2026 · namespace: check a recursive bind mount for mount namespace loops0Monitor
- Later →CVE-2026-98991Oct 23, 2026 · namespace: queue a mount only once for mount notifications31Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| Linux Linux | 18902a23ef36f83d32bafc58ae2484e6bb4bb8ef | Vendor (CNA) |
| Linux Linux | 32bf92416614a1e3ff3524fc6b780259c7aad3ef | Vendor (CNA) |
| Linux Linux | 361f59e7f3f9a219fb5567bf9abc8482a154a399 | Vendor (CNA) |
| Linux Linux | 3f55f71291e4332983cd63b288d1f2be3c9c08fc | Vendor (CNA) |
| Linux Linux | 4.10 | Vendor (CNA) |
| Linux Linux | 4.11 | Vendor (CNA) |
| Linux Linux | 4.2 | Vendor (CNA) |
| Linux Linux | 4.5 | Vendor (CNA) |
| Linux Linux | 6e4012e571867868b545c91ca9d6095fdb709907 | Vendor (CNA) |
| Linux Linux | cda0c4e502a0f74a191471ce100fb061e5ab35d6 | Vendor (CNA) |
| Linux Linux | d73f04e92c1aab78d96ac6cadb234c8a3a373d22 | Vendor (CNA) |
| Linux Linux | f6394281834492c6516a405a348b545ae698a331 | Vendor (CNA) |
| azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 | Release Notes | Microsoft (MSRC) |
| azl3 kernel 6.6.159.1-1 on Azure Linux 3.0 | 6.6.161.1-1 · Release Notes | Microsoft (MSRC) |
| debian:linux | 6.12.113-1 · Debian:13 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
- Published
- Fix recordedsame day
- TodayNov 10, 2026+18 d
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
National notice (Türkiye Cybersecurity Directorate / USOM)
Official security notices citing this record; remediation advice is on the agency's page.
- TR-26-1390 · Oct 26, 2026(Linux Kernel Güvenlik Bildirimi)
Technical details
No CVSS vector for this record, so attack conditions can't be derived.
Weakness class (CWE)
—
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Change log
- Exploit maturity— → none
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (7 more)Show less
- git.kernel.org/stable/c/32bf92416614a1e3ff3524fc6b780259c7aad3ef
- git.kernel.org/stable/c/361f59e7f3f9a219fb5567bf9abc8482a154a399
- git.kernel.org/stable/c/3f55f71291e4332983cd63b288d1f2be3c9c08fc
- git.kernel.org/stable/c/6e4012e571867868b545c91ca9d6095fdb709907
- git.kernel.org/stable/c/cda0c4e502a0f74a191471ce100fb061e5ab35d6
- git.kernel.org/stable/c/d73f04e92c1aab78d96ac6cadb234c8a3a373d22
- git.kernel.org/stable/c/f6394281834492c6516a405a348b545ae698a331
Vendor advisories and official records. Exploit/PoC links are deliberately left out.